Thursday afternoon found Danielle Guigli performing a familiar routine: squeezing her Jeep Cherokee into a tight space on Newbury Street, forced by the city’s parking restrictions to hop from one metered space to another all day long.

So the 24-year-old real estate broker was delighted at the prospect of a new mobile app, called Haystack, that will alert her to nearby parking spaces when they become available.

“That would be awesome,” said Guigli, who was not put off by the $3 fee to lock in a space freed up by another Haystack user. “I’d do it.”

But the real owner of those parking spaces, the City of Boston, is not so excited.

Haystack debuts in Boston on Tuesday. Users receive an electronic notification when someone else in the Haystack network is about to leave a nearby public metered or free parking space. The driver giving up the spot gets $2.25, and Haystack gets 75 cents for brokering the exchange.

But the Walsh administration contends Haystack essentially will be selling property it doesn’t own — city parking spaces — and profiting from a public asset.

“That has implications that at first blush are alarming to us,” said Walsh’s chief of staff, Daniel Koh. “When a space is available, it should be available to anyone, regardless of whether they have extra money to pay for it.”

Parking has long been a sore point for Boston residents and visitors alike. Mayor Martin J. Walsh has given his blessing to the longstanding tradition by residents of congested neighborhoods of using orange cones and folding chairs to save the spaces they shovel out after snow emergencies. But Koh said the administration is worried Haystack could escalate parking tensions by giving unfair advantages to drivers who can afford smartphones and the service’s fees.

Haystack’s 24-year-old founder, who says his app is an innovative solution to one of urban living’s great frustrations, contends the company is not selling public property at all. Rather, it is selling information about public parking — specifically, when spaces are about to open up.

“There’s no sale of physical property,” Eric Meyer said. “This is neighbors exchanging information for a fee, and they have every right to do that. What you’re really paying for is convenience.”

Launched in Baltimore in May, Haystack works like this:

An occupant of a parking space alerts other app users the spot is opening up. The first driver to respond gets to claim the space, then receives precise directions and a description of the departing vehicle. The holder of the parking space declares how long he will wait around for his successor, who pays only when the two exchange spots.

Other companies with similar apps are running into trouble in another American city with a tech-savvy reputation and nightmare parking: San Francisco. City attorney Dennis Herrera has threatened to fine three services — MonkeyParking, Sweetch, and ParkModo — if they do not cease operations, accusing them of “hold[ing] hostage on-street public parking spots for their own private profit.”

“It creates a predatory private market for public parking spaces that San Franciscans will not tolerate,” Herrera said in June. “Worst of all, it encourages drivers to use their mobile devices unsafely — to engage in online bidding wars while driving.”

MonkeyParking and ParkModo recently disabled their services, but Sweetch founder Aboud Jardaneh said Thursday that his company had not received a formal cease-and-desist order and has no plans to halt operations.

Like Haystack, Sweetch helps drivers find parking spaces for a flat fee, $5. MonkeyParking auctions off spaces to the highest bidders. ParkModo, meanwhile, has taken to hiring drivers — at $13 per hour — to occupy street spaces at peak hours in busy neighborhoods as a way of increasing app usage.

Boston is itself using technology to make parking a little less stressful. In December, it rolled out an app called Parker that uses sensors to show which of 330 spaces in the Innovation District are available.

The city is also soliciting bids from contractors for a system that will allow drivers to pay for parking meters electronically via a smartphone app, instead of having to fish for quarters in-between seats. The MBTA has allowed commuter rail passengers to pay for parking by phone since 2008.

Unlike San Francisco, Boston is taking a conciliatory tone with Haystack Mobile Technologies, based in Baltimore. Rather than try to prevent it from operating, Koh said, the administration would like to work with Meyer to see if Haystack’s technology could help alleviate Boston’s parking problems — without profiting from the sale of parking or giving some drivers an unfair advantage.

In theory, Haystack drivers could profit by finding parking spaces on their own and then selling them. At a minimum, Meyer said, motorists can recoup some of what they paid Haystack to get the spot in the first place by simply reselling it when they leave.

After circling Boston Common twice before finding a metered space on Park Street Thursday, 24-year-old John Spencer of Quincy was excited by the prospect of an app like Haystack. “Oh, that’d be cool,” he said. But he seemed deterred by the $3 fee.

On Newbury Street, Jim Hodgson, who gave his age at “just under 70,” was more decisive: In from South Dartmouth to shop, Hodgson bragged he had a special touch for finding parking and saw no need to pay for a tip about an open space.

“I have the Force,” Hodgson cracked, referring to the fictional power from the “Star Wars” films.